Toxic causes of dementia include exposure to heavy metals such as lead, mercury and aluminum as well as to carbon monoxide and solvents. Autoimmune conditions include such entities as multiple sclerosis, systemic lupus erythematosus, Behcet's disease and Sjogren's syndrome. These conditions share broadly similar cognitive effects giving rise to impairments with subcortical features. Individuals are often affected at a relatively young age. Optimal preventative strategies include avoidance of toxic substances. Comprehensive neuropsychological assessment is valuable not only diagnostically and for monitoring but also to identify the patients' strengths and weaknesses, so that compensatory strategies can be recommended.